Seat back



FIG. 1 is a left perspective view of the seat back;

FIG. 2 is a right perspective view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side elevational view thereof, the left side being a mirror image thereof;

FIG. 6 is a rear elevational view thereof; and,

FIG. 7 is a front elevational view thereof.

The broken line portion of the figure drawings is included to show portions of the article that forms no part of the claimed design. 

CLAIM The ornamental design for a seat back, as is shown and describe herein. 